NAME

sys/sem.h - XSI semaphore facility

SYNOPSIS

#include<sys/sem.h>

DESCRIPTION

The <sys/sem.h> header shall define the following constants and
structures.
Semaphore operation flags:
SEM_UNDO
Set up adjust on exit entry.
Command definitions for the semctl() function shall be provided as
follows:
GETNCNT
Get semncnt.
GETPID Get sempid.
GETVAL Get semval.
GETALL Get all cases of semval.
GETZCNT
Get semzcnt.
SETVAL Set semval.
SETALL Set all cases of semval.
The semid_ds structure shall contain the following members:
structipc_permsem_perm Operation permission structure.
unsignedshortsem_nsems Number of semaphores in set.
time_tsem_otime Last semop
() time.
time_tsem_ctime Last time changed by semctl
().
The pid_t, time_t, key_t, and size_t types shall be defined as
described in <sys/types.h> .
A semaphore shall be represented by an anonymous structure containing
the following members:
unsignedshortsemval Semaphore value.
pid_tsempid Process ID of last operation.
unsignedshortsemncnt Number of processes waiting for semval
to become greater than current value.
unsignedshortsemzcnt Number of processes waiting for semval
to become 0.
The sembuf structure shall contain the following members:
unsignedshortsem_num Semaphore number.
shortsem_op Semaphore operation.
shortsem_flg Operation flags.
The following shall be declared as functions and may also be defined as
macros. Function prototypes shall be provided.
intsemctl(int,int,int,...);intsemget(key_t,int,int);intsemop(int,structsembuf*,size_t);
In addition, all of the symbols from <sys/ipc.h> shall be defined when
this header is included.
Thefollowingsectionsareinformative.

APPLICATIONUSAGE

None.

RATIONALE

None.

FUTUREDIRECTIONS

None.

SEEALSO

<sys/ipc.h> , <sys/types.h> , semctl(), semget(), semop()

COPYRIGHT

Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online
at http://www.opengroup.org/unix/online.html .